Chap. Y. 
TAILS OF MONKEYS. 
307 
been made colonel of the new national guard. They 
had been obtained with great difficulty in the forests 
which cover the low lands, near the principal mouth of 
the Japura, about thirty miles from Ega. It was the first 
time I had seen this most curious of all the South Ame- 
rican monkeys, and one that appears to have escaped 
the notice of Spix and Martins. I afterwards made a 
journey to the district inhabited by it, but did not then 
succeed in obtaining specimens ; before leaving the 
country, however, I acquired two individuals, one of 
which lived in my house for several weeks. 
The scarlet-faced monkey belongs, in all essential 
points of structure, to the same family (Cebidse) as 
the rest of the large-sized American species ; but it 
differs from all its relatives in having only the rudi- 
ment of a tail, a member which reaches in some allied 
kinds the highest grade of development known in the 
order. It was so unusual to see a nearly tailless monkey 
from America, that naturalists thought, when the first 
specimens arrived in Europe, that the member had been 
shortened artificially. Nevertheless, the Uakari is not 
quite isolated from its related species of the same family, 
several other kinds, also found on the Amazons, forming 
a graduated passage between the extreme forms as 
regards the tail. The appendage reaches its perfection 
in those genera (the Howlers, the Lagothrix and the 
Spider monkeys) in which it presents on its under-surface 
near the tip a naked palm, which makes it sensitive and 
useful as a fifth hand in climbing. In the rest of the 
genera of Cebidae (seven in number, containing thirty- 
eight species), the tail is weaker in structure, entirely 
